1. Field of the Invention
This invention relates to a disk cartridge wherein the main body of the cartridge containing a disk on which predetermined information signals are recorded, such as an optical disk or a magnetic disk, and including a window for exposing a portion of the disk to the outside, is provided with a slide shutter adapted for opening and closing the window. More particularly, it relates to such a disk cartridge in which a torsion spring is provided within the main body of the cartridge for urging the shutter in a window closure direction.
2. Related Art Statement
It is known to provide a disk cartridge of the type wherein the main body of the cartridge contains a disk on which predetermined information signals are recorded, such as an optical disk or a magnetic disk, and which includes a window for exposing a portion of the disk to the outside, with a slide shutter adapted for opening and closing the window. It is further known to provide a torsion spring within the main body of the cartridge for urging the shutter in the window closure direction. Such a cartridge is disclosed, for example, in the Japanese Laid-open Patent Publication NO. 169379/1983 or U.S. Pat. No. 4,550,354.
In the above described prior-art disk cartridge, the torsion spring urging the slide shutter in this manner is mounted within the space of a corner surrounded by a disk container provided in the main body of the cartridge, the front wall and one side wall of the main body. One end of the torsion spring extends from the central torsion coil to engage a corner where the front wall intersects the one side wall, while the other end of the torsion spring extends from the other end of the torsion coil to engage one lateral side of the shutter. In following up the opening and closing movement of the shutter, the torsion spring is flexed throughout the extent of the corner of the main body of the cartridge such that it is not possible to provide threaded boss projections at the corner of the main body for interconnecting the upper and lower halves that make up the main body.
For this reason, the upper and lower halves of body of the cartridge are connected together by an using an adhesive or by ultrasonic welding method. Should either such connecting method be used, the upper and lower halves cannot be separated from each other, so that it becomes extremely difficult to replace the disk even if the disk is scratched or otherwise injured and hence unable to be used for regular recording and/or reproducing operations. In addition, it becomes difficult to re-use the main body of the cartridge.
In view of these inconveniences, and with reference to FIG. 1, it has been proposed in a prior patent application of the present assignee to attach a shutter 104 to a slide member 103 which is slidably supported by a main body of the cartridge 101 and having a first rack gear 102 on one lateral surface of the slide member 103, with the shutter 104 being slidable with respect to the main body of the cartridge 101. A second stationary rack gear 105 is attached to the main body of the cartridge 101 in opposition to the first rack gear 102 and a pinion 106 is interposed between these rack gears 102 and 105. The shutter 104 for opening or closing a window 107 provided in the main body of the cartridge 101 is biased in a direction to close the window 107 by means of a torsion spring 108 which is positioned within the space of a corner of the main body of the cartridge 101. The Torsion spring's end are captured between a support point 110 attached to the main body 101 and a spring holder 109 rotatably fitted to the pinion 106. That is, the torsion spring 108 has the end of one arm 108b extending from a torsion coil 108a and retained by the support 110 provided at the corner of the main body of the cartridge 101 and has the end of the other arm 108c retained by the spring holder 109.
During the time the disk is not used, the pinion 106 interposed between the first rack gear 102 of the slide member 103 and the second rack gear 105 of the main body of the cartridge 101 is turned relative to the second rack gear 105 under the force of the torsion spring 108, in such a manner that the slide member 103, meshing with the pinion 105, is thrust and slid so that the window 107 is closed by the shutter 104 attached to the slide member 103.
During the time the disk is in use, the shutter 104 is slid by the shutter opening and closing system of a recording and/or reproducing apparatus. For example, the slide member 103 is slid to cause the pinion 106 to be turned relative to the second rack gear 105 of the main body of the cartridge 101 by the first rack gear 102 provided to the slide member 103. The pinion 105 is turned at such time with a rolling motion so that the horizontal distance traversed by the pinion 105 as it is turned is approximately one half that traversed by the slide member 103, such that, when the shutter 104 is slid to a position of completely opening the window 107, the pinion 106 is positioned intermediate between the window 107 and one side wall of the main body of the cartridge 101. In such a manner, the flexing shifting of the torsion spring 108 installed between the pinion 106 and the main body of the cartridge 101, that is, the horizontal distance traversed by the end of the arm 108c during flexure of the torsion spring 108, is about one half the slide stroke of the slide member 103, so that there may be provided at the corner of the main body of the cartridge 101 a space sufficient to accommodate threaded boss projections 111 for interconnecting the upper and lower halves of the main body of the cartridge 101.
In the aforementioned conventional disk cartridges, the ends of the torsion spring for biasing the shutter are secured. Thus, in the disk cartridge described in the present applicant's prior application, the torsion coil 108a of the torsion spring 108 pivots with the opening and closing movement of the shutter 104 about the supporting point O of the arm 108a with a trajectory being on a circumference of a circle having the arm 108b as a radius.
The main body of the cartridge 101 has the shape of a square inscribed by a circle that is the contour of the disk accommodated therein, in order to minimize its size. Within the main body of the cartridge 101, rib sections 113 are formed for encircling the disk 112 along its outer periphery for restricting the disk movement within the main body of the cartridge 101 in order to protect the disk 112. Thus, in the disk cartridge shown in FIG. 1, the torsion coil 108a is closest to the rib section 113 when the torsion spring 108 is shifted as a result of the shutter movement to a position at a minimum distance between the rib section 113 and the support 110. At this time, there is the risk of the torsion coil 108a conflicting with the rib section 113 if the dimensional tolerances in casting the rib section 113 and the support 110 or in producing the torsion spring 108 act in concert for reducing the aforementioned minimum distance. Should the torsion coil 108a conflict with the rib section 113, not only the desired spring pressure of the torsion spring 108 or the smooth opening and closure of the shutter 104 cannot be obtained, but also the movement of the torsion spring and the pinion 106 is impeded. This results in inhibition of the shutter movement for window opening or closure and destruction of the main body of the cartridge 101. In the case of a disk cartridge which is devoid of the rib sections 113, the torsion coil of the spring may conflict with the outer periphery of the disk thus giving rise to a similar phenomenon and possibly to disk destruction.
In order to eliminate such inconvenience and to provide the a trajectory for the torsion coil 108a of the torsion spring 108 as it shifted with the window opening and closing movement of the shutter 104 as indicated by Y in FIG. 1, it may be contemplated to make the length of the arm 108b, supported by the main body of the cartridge 101, longer than that of the other arm 108c as indicated by a dotted line in FIG. 1 and to shift the position of the support 110 retaining the end of the one arm 108b towards the front side of the main body of the cartridge 101.
However, when the torsion spring 108 has such a disymmetrical shape, attachment of the torsion spring becomes increasingly difficult especially when employing an automatic assembling device.